Fibrous nonwoven web materials are in wide use in a number of applications including but not limited to absorbent structures and wiping products, many of which are disposable. In particular, such materials are commonly used in personal care absorbent articles such as diapers, diaper pants, training pants, feminine hygiene products, adult incontinence products, bandages and wiping products such as baby and adult wet wipes. They are also commonly used in cleaning products such as wet and dry disposable wipes which may be treated with cleaning and other compounds which are designed to be used by hand or in conjunction with cleaning devices such as mops. Yet a further application is with beauty aids such as cleansing and make-up removal pads and wipes.
In many of these applications, three-dimensionality and increased surface area are desirable attributes. This is particularly true with body contacting materials for the aforementioned personal care absorbent articles and cleaning products. One of the main functions of personal care absorbent articles is to absorb and retain body exudates such as blood, menses, urine and bowel movements. By providing fibrous nonwovens with hollow projections, several attributes can be achieved at the same time. First, by providing projections, the overall laminate can be made to have a higher degree of thickness while minimizing material used. Increased material thickness serves to enhance the separation of the skin of the user from the absorbent core, hence improving the prospect of drier skin. By providing projections, land areas are created between the projections that can temporarily distance exudates from the high points of the projections while the exudates are being absorbed, thus reducing skin contact and providing better skin benefits. Second, by providing such projections, the spread of exudates in the finished product may be reduced, hence exposing less skin to contamination. Third, by providing projections, the hollows can, themselves, serve as fluid reservoirs to temporarily store body exudates and then later allow the exudates to move vertically into subjacent layers of the overall product. Fourth, by reducing overall skin contact, the fibrous nonwoven laminate with such projections can provide a softer feel to the contacted skin thereby enhancing the tactile aesthetics of the layer and the overall product. Fifth, when such materials are used as body contacting liner materials for products such as diapers, diaper pants, training pants, adult incontinence products and feminine hygiene products, the liner material also serves the function of acting as a cleaning aid when the product is removed. This is especially the case with menses and lower viscosity bowel movements as are commonly encountered in conjunction with such products. Here again, such materials can provide added benefit from a cleaning and containment perspective.
In the context of cleaning products, again the projections can provide increased overall surface area for collecting and containing material removed from the surface being cleaned. In addition, cleaning and other compounds may be loaded into the hollow projections to store and then upon use, release these cleaning and other compounds onto the surface being cleaned. Other attempts have been made to provide fibrous nonwoven webs which will provide the above-mentioned attributes and fulfill the above-mentions tasks. One such approach has been the use of various types of embossing to create three-dimensionality. This works to an extent, however high basis weights are required to create a structure with significant topography. Furthermore, it is inherent in the embossing process that starting thickness is lost due to the fact that embossing is, by its nature, a crushing and bonding process. Furthermore, to “set” the embossments in a nonwoven fabric the densified sections are typically fused to create weld points that are typically impervious to fluid. Hence a part of the area for fluid to transit through the material is lost. Also, “setting” the fabric can cause the material to stiffen and become harsh to the touch.
Another approach to provide the above-mentioned attributes has been to form fibrous webs on three dimensional forming surfaces. The resulting structures typically have little resilience at low basis weights (assuming soft fibers with desirable aesthetic attributes are used) and the topography is significantly degraded when wound on a roll and put through subsequent converting processes. This is partly addressed in the three dimensional forming process by allowing the three dimensional shape to fill with fiber. However, this typically comes at a higher cost due to the usage of more material and at the cost of softness, as well as the fact that the resultant material becomes aesthetically unappealing for certain applications.
Another approach to provide the above-mentioned attributes has been to aperture a fibrous web. Depending on the process, this can generate a flat two dimensional web or a web with some three dimensionality where the displaced fiber is pushed out of the plane of the original web. Typically, the extent of the three-dimensionality is limited, and under sufficient load, the displaced fiber may be pushed back toward its original position resulting in at least partial closure of the aperture. Aperturing processes that attempt to “set” the displaced fiber outside the plane of the original web are also prone to degrading the softness of the starting web. Another problem with apertured materials is that when they are incorporated into end products as this is often done with the use of adhesives, due to their open structure, adhesives will often readily penetrate through the apertures in the nonwoven from its underside to its top, exposed surface, thereby creating unwanted issues such as adhesive build-up in the converting process or creating unintended bonds between layers within the finished product. As a result, there is a still a need for both a material and a process and apparatus which provide three-dimensional characteristics that meet the aforementioned needs.